Heat lamp chicks

[Sophia5]

I have recently been told (from a number of different people) about some severe pecking from one hen to another- to the point of of bleeding and extreme feather loss. These stories have all come from chickens who had been raised under a heat lamp. I wonder if this is a coincidence or whether anyone else has ever drawn the same conclusion?
The ordinary reasons for chickens to really bully other hens (I'm talking more than just the normal 'Pecking order') such as cramped conditions, under-feeding, not enough light etc. don't apply to these cases as they are all from free-range, well-fed chickens.
What do you think?
Is it just a random thing or are we humans socially messing up chickens by not providing for them a natural environment? i.e. - a caring mother hen who teaches them the rules of society?

Would love to hear your opinions on this

 

[FVRM]

I think EVERY chicken owned here has been raised under a heat lamp. Most come from hatcheries where they use heat lamps and even if it's locally we still use heat lamps. It depends on the personality of the chicken, some are natural bullies.